<template>
  <div class="spec-preview">
    <img :src="selectImage" />
    <div class="event"  @mousemove="imgMove"></div>
    <div class="big">
      <img :src="selectImage"  ref="big" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    data() {
      return {
        current: 0,
      }
    },
    props: {
      skuImageList:{
        type: Array,
        default() {
          return []
        }
      }
      
    },
    computed: {
      selectImage() {
        this.$bus.$on('sliderClickBrother', i => this.current = i)
        return this.skuImageList && this.skuImageList.length && this.skuImageList[this.current].imgUrl 
      }
    },

    methods: {
      imgMove() {
        // 获取DOM元素
        let mask = this.$refs.mask
        let big = this.$refs.big
        // 获取鼠标离x,y轴距离
        let x = event.offsetX - mask.offsetWidth / 2
        let y = event.offsetY - mask.offsetHeight / 2
        // 约束鼠标
        if(x <= 0) x = 0;
        if(y <= 0) y = 0;
        if(x >= mask.offsetWidth) x = mask.offsetWidth;
        if(y >= mask.offsetHeight) y = mask.offsetHeight;
        // 修改mask遮罩层
        mask.style.left = x + 'px'
        mask.style.top = y + 'px'
        // 修改大图片
        big.style.left = -2 * x + 'px'
        big.style.top = -2 * y + 'px'
      }
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>